Metabolators



July 16, 1963 l. STREIMER 3,097,638

METABOLATORS Filed Feb. 27, 1961 United States Patent Office 3,097,638 Patented July 16, 1963 3,097,638 METABOLATORS Irving Streimer, Bellevue, Wash., assignor to Boeing Airplane Company, Seattle, Wash., a corporation of Delaware Filed Feb. 27, 1961, Ser. No. 91,711 6 Claims. c1. 128-2.07)

This invention relates to improvements in metabolator apparatus for measuring oxygen consumption rate and related breathing characteristics. The invention is herein illustratively described by reference to the presently preferred embodiment thereof; however, it will be recognized that certain modifications and changes therein with respect to details may be made without departing from the underlying essentials involved.

A broad object hereof is to provide a simple, reliable and accurate metabolator of light-weight, compact construction. Specifically, it is desired to provide such a device of portable form which can be worn on or carried by the patient during physical activities in which the patient is required to be ambulatory.

A specific object is to provide a metabolator of the type in which oxygen from a primary source is introduced into a closed-circuit breathing system wherein exhaled oxygen is recirculated and exhaled carbon dioxide and moisture are trapped. A related object is to provide such a metabolator wherein oxygen supply rate is controlled by demand regulator apparatus insuring oxygen supply at predetermined pressure referenced to atmosphere, whereby normal environmental breathing conditions are simulated as closely as possible.

Still another specific object is to provide a metabolator incorporating a simple and reliable, high-output breathing detector operable to detect breathing frequency and breath cycle form, and to do this without adding materially to the cost, weight or bulk of the metabolator.

Still another object is to provide a simple, direct-indicating and reliable means for quantitatively indicating oxygen consumption in such a device.

In accordance with one feature of the invention, oxygen from a bottle or other primary source is fed at a demand-regulated rate into the closed-circuit breathing system by means of a differential pressure actuated valve incorporated in the supply line and actuated by a diaphragm or the like sensitive to the difference between atmospheric pressure and internal breathing apparatus pressure presented to the patient. The device further includes a means to indicate directly oxygen consumption during any selected test period, such means preferably comprising a Bourdon tube pressure gauge connected in the high-pressure side of the demand regulator valve passage and calibrated in the particular apparatus to measure quantity of oxygen consumed.

A further feature resides in the provision of a thermistor element breathing detector incorporated in a breathing passage of the apparatus, and preferably on the lowpressure side of the exhalant check valve in or adjacent to the patient utilization device, which thermistor produces a relatively strong output signal having a waveform and magnitude determined by exh-alant temperature variations and closely representative of those breathing characteristics of primary interest in metabolism tests.

These and other features, objects and advantages of the invention will become more fully evident from the following description thereof by reference to the accompanying drawings.

FIGURE 1 is a schematic diagram of the improved portable metabolator.

FIGURE 2 is a somewhat simplified longitudinal sectional view taken through the main unit which includes the oxygen supply, the carbon dioxide and moisture filter, the demand regulator, oxygen consumption gauge means and portions of the closed-circuit breathing system.

Referring to FIGURE 1, the patient utilization device 10 in this case comprises a face mask or mouthpiece which is connected to the tube 12 having the branching portions 14 and 16. The branch 14 comprises an oxygen supply conduit having a check valve 18 therein which excludes exhalant from the tube 14' beyond the check valve while permitting inflow of oxygen from tube 14 when the patient inhales. The tube 16 comprises the exhalant passage with a check valve 20 therein which prevents exhaled gases in the tube 16' beyond the check valve from flowing back to the patient utilization device. As shown by the arrows, when the patient inhales the check valve 18 is drawn open and fresh oxygen is drawn into the utilization device, check valve 20 remaining closed, whereas when the patient exhales valve 18 is closed and the check valve 20 is forced open and permits exhaled gases to flow into the tube 16'. A rubber-like breathing bag or accumulator 22 is connected to the tube 16 which extends to the trap or filter 24 containing soda lime or other substance for trapping carbon dioxide and preferably also moisture. As is conventional, the breathing bag 22 stores exhalant gases, as an accumulator, and feeds those gases slowly through the filter 24 at a reduced rate which permits effective absorption of the carbon dioxide and moisture.

From the filter 24 unused oxygen which passes through the soda lime bed is conducted by a tube or passage 26 to the inhaler tube 14' through the low-pressure chamber 28 of a demand regulator unit 30. This demand regulator unit comprises a control valve 32 seated in the port of an inlet passage or pipe 34 connected to the pressurized oxygen bottle 36 or other primary source of oxygen. The valve 3 2 is mounted on a support rod 38 and is urged toward closed position by a return spring 40. The end of the rod 38 opposite from the valve 32 is pivotally connected to the short lever arm 42 of a bell crank pivoted at 44 on a fixed support in the demand regulator. A relatively long lever arm 46 of this bell crank is pivotally connected to a large diaphragm 48 which divides the demand regulator housing 30 into the oxygen supply chamber 28 and an atmosphere chamber 50 which communicates with the ambient atmosphere (or other pressure reference in special cases) through the vent or opening 5-2. If the pressure in the supply chamber 28 drops appreciably below that in the atmosphere chamber 50 the bell crank opens the valve 32 and additional oxygen flows from the primary source 36 into the chamber 28 for presentation to the patient. Thus, the oxygen supply pressure presented to the patient is substantially ambient atmospheric pressure, or more specifically is a pressure which is only slightly lower than the pressure in chamber 50.

A Bourdon tube gauge or other pressure gauge 54 communicating with the high-pressure side of the demand regulator valve is calibrated in the apparatus to indicate, by a cumulative change of pressure over a period of time, the amount of oxygen consumed in that period. If temperature conditions change widely during the test period, temperature compensation may be required in order to correct the readings of the oxygen consumption gauge 54. Therefore, it is also desirable in some cases to provide a thermometer 56, likewise in communication with the high-pressure side of the demand regulator valve and from which correction data may be derived. In most tests, however, the test duration may be so short that no appreciable temperature change occurs suflicient to require temperature corrections.

Referring now to the details shown in FIGURE 2, the unit as thus far described is preferably mounted in a casing 60, except for the patient utilization device and any necessary flexible tubes 14-, 14 and 16, 16", along with the breathing bag 22. The trap 24 comprises an annular cup the open side of which is clamped against a seal 24a surrounding the sleeve 62 which houses the oxygen bottle 36. The cup is clamped in this position by a ring 64 which threads onto the outer end of the sleeve 62. A conventional insert valve 66 in the discharge end of the oxygen bottle is opened when the oxygen bottle is inserted and the two lugs 68 on the projecting valve fitting engage a cam 70 mounted in the housing 60, in order to be actuated by the cam as the bottle is turned through a predetermined angle about its longitudinal axis. This type of valve actuating system is known. When the valve 66 is opened, oxygen under high pressure is delivered into the passageways 72 which lead to the demand regulator valve 34 and to the inlet of the Bourdon tube pressure gauge 54.

The demand regulator section or unit 32 comprises an axial extension of the section which carries the coaxially arranged filter and oxygen supply bottle. The extreme end face of the unit comprises a transparent viewing screen 80 through which the indicator needle 54a of the Bourdon tube pressure gauge 54 may be seen. The Bourdon tube is mounted physically in the atmosphere chamber 50 adjacent to the atmosphere side of the diaphragm 48. An apertured membrane stop 82 is bowed convexly toward the Bourdon tube gauge and acts as a protective barrier between the Bourdon tube gauge and the diaphragm, preventing extreme flexure of the diaphragm toward the Bourdon tube gauge from damaging either.

The demand regulator valve mechanism is mounted in the interior space 2.8 with-in the housing 60 between the diaphragm 48 and the filter-oxygen bottle unit. Oxygen emerging from the soda lime trap flows to an inlet 84 into the chamber 28 and from this chamber flows, along with fresh oxygen admitted through the valve 32, out the port 86 to the supply tube '14.

The thermometer 56 is mounted on the end of the oxygen supply bottle 36 facing from the end of the unit opposite that occupied by the Bourdon tube pressure gauge 54. I

As a further feature, a thermistor unit 90 is mounted the exhalant passage 16, 16, beyond the check valve 20. It is connected in a thermistor amplifier circuit 92 which operates a recording oscillograph 94. Being sensitive to temperature, this thermistor produces an electrical signal which is related to breath exhalant temperature and thereby varies in amplitude as the patient breathes. With each exhalation the signal increases in amplitude initially and then drops in amplitude as the exhalation cycle terminates. The drop in amplitude is, of course due to the radiation and absorption of heat of the exhaled gases as they are held in the tube 16' pending ultimate flow to the filter unit 24. The recording oscillograph trace thereby shows the breathing frequency, amplitude and pattern of the patient. This data when considered along with the quantity of oxygen consumed during the test has important diagnostic value as will be readily noted.

This invention enables a physician to determine the minute-by-minute rate of oxygen consumption in the case of blue babies, in the case of adults being diagnosed for glandular, heart and other conditions and in the case of operative and postoperative therapy, giving an indication of the patients vitality. Also, it may be used in anesthesiology wherein gases may be premixed and fed to the patient at his own demand rate, thereby avoiding the latitude of hunting which normally occurs in maintaining a patient at a given level of anesthesia. It may also be used to test the physical well being of an astronaut during space flight. These and other uses and aspects of the invention will be recognized by those skilled in the art, based on the present disclosure.

I claim as my invention:

1. A metabolator comprising a closed-circuit breathing system including a patient utilization device, a carbon dioxide absorber unit having input and output, a demand regulator unit having a low-pressure flow space and a high-pressure fiow space therein, an exhaling duct connecting said patient utilization device to said input, means connecting said low-pressure flow space to said output, an inhaling duct connecting said patient utilization device to said low-pressure flow space, a source of compressed oxygen connected to said high-pressure flow space, said demand regulator unit further including a passage interconnecting said How spaces, a valve normally closing said passage, and a valve-actuating device including means responsive to the difierential of ambient atmospheric pressure and pressure in said low-pressure flow space and operable to open said valve when such latter pressure drops by a predetermined amount below such ambient atmospheric pressure, thereby continuously to provide oxygen at substantially atmospheric pressure to the patient, and means to measure the quantity of oxygen consumed by the patient.

2. The metabolator defined in claim 1, wherein the last-mentioned means comprises a pressure-sensitive indicator responsively connected to the high-pressure flow space to measure the change of pressure of oxygen therein over a predetermined test period.

3. The metabolator defined in claim 2, and a thermoelectric element mounted in the exhaling duct, and associated indicator circuit means in which said thermoelectric element is electrically connected, including an indicator responsive to the electric pulsations inducted in said element by temperature cycles accompanying breath exhalations from the patient.

4. The metabolator defined in claim 3, wherein the thermoelectric element comprises a thermistor and the last-mentioned indicator includes a means responsive to thermistor current variations.

5. A metabolator comprising a closed-circuit breathing system including a patient utilization device, a carbon dioxide absorber unit having input and output, a demand regulator unit having a low-pressure flow space and a high-pressure flow space therein, an exhaling duct connecting said patient utilization device to said input, means connecting said low-pressure fiow space to said output, an inhaling duct connecting said patient utilization device to said low-pressure fiow space, a source of compressed oxygen connected to said high-pressure flow space, said demand regulator unit further including a passage interconnecting said flow spaces, a valve normally closing said passage, and a valve-actuating device operable to maintain oxygen pressure in said low-pressure flow space by opening said valve in response to a drop of pressure therein, and means to measure the quantity of oxygen consumed by the patient, comprising a pressure-sensitive indicator responsively connected to the 5 6 high-pressure flow space to measure the change of pres- 2,893,3 81 Black July 7, 1959 sureof oxygen therein over a medetermined test period. 2,916,033 Coleman Dec. 8, "1959 6. The met-abolator defined in claim 5, and a theimo- 2,981,911 Wamick Apr. 25, 1961 electric element mounted in the exhaling duct, and associated indicator circuit means in which said thermuelec- 5 FOREIGN PATENTS tric element is electrically connected, including an indicator [responsive to the electric pulsations induced said element by temperature cycles accompanying breath exhal-ations from the patient.

References Cited in the file of this patent 10 Leach: 59191199, P 15,

UNITED STATES PATENTS 1,550,335 Benedict Aug. 18, 1925 848,725 Great Britain Sept. 21, 1960 OTHER REFERENCES 

1. A METABOLATOR COMPRISING A CLOSED-CIRCUIT BREATHING SYSTEM INCLUDING A PATIENT UTILIZATION DEVICE, A CARBON DIOXIDE ABSORBER UNIT HAVING INPUT AND OUTPUT, A DEMAND REGULATOR UNIT HAVING A LOW-PRESSURE FLOW SPACE AND A HIGH-PRESSURE FLOW SPACE THEREIN, AN EXHALING DUCT CONNECTING SAID PATIENT UTILIZATION DEVICE TO SAID INPUT, MEANS CONNECTING SAID LOW-PRESSURE FLOW SPACE TO SAID OUTPUTS, AN INHALING DUCT CONNECTING SAID PATIENT UTILIZATION DEVICE TO SAID LOW-PRESSURE FLOW SPACE, A SOURCE OF COMPRESSED OXYGEN CONNECTED TO SAID HIGH-PRESSURE FLOW SPACE, SAID DEMAND REGULATOR UNIT FURTHER INCLUDING A PASSAGE INTERCONNECTING SAID FLOW SPACES, A VALVE NORMALLY CLOSING SAID PASSAGE, AND A VALVE-ACTUATING DEVICE INCLUDING MEANS RESPONSIVE TO THE DIFFERENTIAL OF AMBIENT ATMOSPHERIC PRESSURE AND PRESSURE IN SAID LOW-PRESSURE FLOW SPACE AND OPERABLE TO OPEN SAID VALVE WHEN SUCH LATTER PRESSURE DROPS BY A PREDETERMINED AMOUNT BELOW SUCH AMBIENT ATMOSPHERIC PRESSURE, THERBY CONTINUOUSLY TO PROVIDE OXYGEN AT SUBSTANTIALLY ATMOSPHERIC PRESSURE TO THE PATIENT, AND MEANS TO MEASURE THE QUANTITY OF OXYGEN CONSUMED BY THE PATIENT. 